The Influence of Boron Additions on Sintering and Mechanical Properties of WC-10Ni Composites

Tungsten carbides are important materials for various application fields. Their unique combination of mechanical properties makes them a good choice for applications demanding high hardness and moderate fracture toughness, such as cutting tools, oil and gas, mining, or machining industries. The microstructure is composed of a hard phase embedded in a soft, ductile binder. Cobalt, which provides the best compatibility with the tungsten carbide phase, is the main binder. However, some issues have been addressed to cobalt during the last decades, including a classification as a critical raw material by the European Commission, a fluctuation of its price due to intense use in batteries, and health and ethical problems. Nickel-based binders are thus a good alternative to cobalt. Nevertheless, their processing requires a higher sintering temperature to achieve full density, which leads to abnormal grain growth and thus reduces mechanical properties. The proposed solution is to use a small amount of boron, which is added during the milling of the powders, to reduce the sintering temperature. After vacuum sintering, the results show that the sintering temperature can be decreased to reach full density. Mechanical properties show enhanced hardness with moderately decreased fracture toughness compared to the parts without boron additions (hardness around 1450 to 1515 HV30 and fracture toughness around 10 to 12 MPa√m). Those results provide a good hardness-to-toughness ratio.